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Modified JK TechTech related bulletin board forum regarding subjects such as suspension, tires & wheels, steering, bumpers, skid plates, drive train, cages, on-board air and other useful modifications that will help improve the performance and protection of your Jeep JK Wrangler (Rubicon, Sahara, Unlimited and X) on the trail.
PLEASE DO NOT START SHOW & TELL TYPE THREADS IN THIS FORUM
I have a 2012 JKU Sahara with 3.5 MC springs and all adjustable control arms. I also have Bilstein 5100 series shocks, Yeti adjustable front track bar, Falcon steering stabilizer, Rockjock tie rod + non flipped drag link, synergy ball joints, and running 35 inch KO2's on methods (For reference, this is my DD and my OD).
I have had this jeep for a couple years now, and ever since I first lifted it I have had serious stability issues... almost to the point where it was dangerous to drive on the highway (at least for me). Now after replacing all of the components listed above, the driving experience has gotten marginally better, but not by much. It has gotten to the point now where I have major bump-steer even at the 40-55 mph range, and some vibrations in the steering wheel. Also, on the highway, I have extremely flighty steering, where any larger vehicle passing me or any major wind has me constantly applying input to the wheel to stay in the lines. I also run my KO2's at 28 PSI on-road. I know some stability issues are to be expected, however my roommate has a 15 Sahara with a 3.5 inch Rock Crawler lift on true bead-locks and his drives like a dream.
After researching for months looking for THE solution, I still don't know for sure. I'm thinking it could be my caster, or maybe I need to drop my TB or CA's. But after a couple of years and a lot of $$$, I'm looking to finally get this resolved so I can go on my over-landing trips out west. Thanks in advance for your help! (Pictures attached below).
Knowing what your caster angle currently is will go a long ways. With full set of adjustable arms there's no reason it shouldn't be dialed in.
Where is the rear raised TB bracket that should be part of that lift? That is one issue. Raising that mount on the axle side will help with the roll center. Up front you could benefit from a high steer kit (DL flip with TB bracket) which would help flatten out those steering angles and help with bump steer.
How old are those ball joints?
You got no bumpstops installed front or rear. Is that intentional? That lift should have come with MC's bumpstops. (that is not contributing to your issue, but noticed it).
Last edited by resharp001; 10-21-2021 at 03:34 PM.
Sorry I forgot to mention my current caster. I just had the shop send me an alignment report. (Pictured below). I had no idea that my caster angle was that low.. it makes more sense now. When I upgraded from my first lift to MC, I bought the arms and springs separately from my local dealer and had him install them but forgot to pick up the rear TB bracket.
Okie dokie.....your caster is definitely low. Adjust those arms so caster is back up over 4* at a minimum (from the factory it's 4.2*) and you will see a pretty big difference. Add a raised bracket in the rear and at the very least consider a high steer kit. You're at the height that most folks will think it's a big improvement. It's not a requirement or anything, but I drove a good while without one and I found it to be a welcome addition.
If you're happy with the front axle's placement, you can simply shorten the upper arms to increase caster (rotate pinion down). The lower arms will position the axle, uppers will adjust caster. The only issue you might have adjusting the uppers right now is then realizing the axle might not be positioned as perfectly as you previously thought. I'd go measure my arms to give you lengths if I could, but I have an aftermarket axle with different caster so it's not apples to apples.
I'm assuming the ball joints are new'er, but not so new that tightest is playing into the "flighty steering".
Last edited by resharp001; 10-21-2021 at 03:54 PM.
Okay I may play around with the uppers and see what I can get them to and then take it to the shop to re-read the caster. The ball joints are probably 18 months old now and have about 20k miles on them.
Yes let me change that, I only have the springs and the full set of arms. The original lift did not have a pitman arm included, and the sway bars stock but on the list of things I need to get replaced.
If you are capable of adjusting the arms yourself then there really is no need to go back for another alignment. You know the current baseline is 3.2*, so you can get a cheap digital angle finder, place it on top of or bottom of the pinion flange, and adjust the arms so that you achieve a 1* difference from whatever the angle finder was previously reading (which will raise caster 1* from your current 3.2 to 4.2). The angle finder is not as exact as an alignment machine and will not reflect the proper reading, but you are really only looking to increase caster 1*. Caster isn't some hard and fast number, but more of an acceptable range, so you don't have to have it be exactly anything. Just get it back up higher. Anywhere in that 4-5* range will work.
(It's when you don't know what the current caster is that it gets a bit more tricky).
If you are capable of adjusting the arms yourself then there really is no need to go back for another alignment. You know the current baseline is 3.2*, so you can get a cheap digital angle finder, place it on top of or bottom of the pinion flange, and adjust the arms so that you achieve a 1* difference from whatever the angle finder was previously reading (which will raise caster 1* from your current 3.2 to 4.2). The angle finder is not as exact as an alignment machine and will not reflect the proper reading, but you are really only looking to increase caster 1*. Caster isn't some hard and fast number, but more of an acceptable range, so you don't have to have it be exactly anything. Just get it back up higher. Anywhere in that 4-5* range will work.
(It's when you don't know what the current caster is that it gets a bit more tricky).
I'll give it a shot and see how it goes. Thanks for the help!
I am having a very similar problem, with my 2014 JKU. It had a 4" lift with 35s when I bought it used about 4 yrs ago. It drove like a dream until this past summer when it developed the death wobble. I used the opportunity to upgrade the mostly stock steering components (Track bar, Drag link, Tie rod, upper & lower ball joints) to Synergy and added a new fox stabilizer. The death wobble went away but it's never drove the same. It use to track great on the freeway with no required steering corrections but now, similar to Keaton, it requires very active steering. It sucks.... Caster is 3.9 & 4.1. I had never noticed it before but I did have some play in the steering box so I adjusted it slight which helped but it still wants to wonder quite a bit. I also videoed the front steering and everything appears locked in with no play when steering back and forth. I'm wondering if it could be that the front axle is no longer exactly centered but I had measured and matched the track bar length before installing.
Any thoughts or ideas? I know this thing can drive so much better than it does now.
10-21-2021, 03:10 PM
Bump-steer and SEVERE stability issues ON JKU
